Molting of megalopae from the blue crab Callinectes sapidus: effects of offshore and estuarine cues

Postlarvae (megalopae) of the blue crab CaUinectes sapidus (Rathbun) are transported from shelf/coastal areas into estuanes where they metamorphose (molt) to the first crab stage This study tested the hypothes~s of Wolcott & DeVries (1994; Mar Ecol, Prog. Ser. 109: 157-163) that metamorphosis is delayed in offshore water and accelerated by cues associated with estuaries. The effects of offshore water, estuarine water, adult blue crab odors, eelgrass Zostera marina and salinity were tested by measuring the time until molting. Test megalopae were collected as they entered an estuary. Molting was slowest in offshore water, faster in estuarine water and fastest in the presence of eelgrass. Adult odors had no effect on molting, however, a decrease in salinity decreased molting time. These results support the hypothesis and indicate blue crab megalopae should preferentially undergo metamorphosis in estuarine seagrass beds.